This invention is generally directed to new toner compositions, and new developer materials as well as the use of such compositions in electrostatographic imaging systems. More specifically, the present invention is directed to toner compositions containing para-halo phenyl carboxylic acids, and salts thereof, which additives impart a positive charge to the toner resin. Toner compositions, that is resin particles and pigment particles, containing the para-halo phenyl carboxylic acids, and salts of the present invention are useful in various electrostatographic imaging systems, including color imaging systems, especially those electrostatographic imaging systems employing Viton fuser roll components as more specifically detailed hereinafter.
Toner and developer compositions containing certain charge control additives, particularly for the purpose of imparting a positive charge toner resins is known in the art. Thus, for example, there is disclosed in U.S. Pat. No. 3,893,935 the use of specific quaternary ammonium compounds as charge control agents for electrostatic toner compositions. In accordance with the disclosure of this patent, certain quaternary ammonium compounds when incorporated into toner materials were found to provide a toner composition which exhibits a relatively high uniform and stable net toner charge when mixed with a suitable carrier vehicle. A similar teaching is contained in U.S. Pat. No. 4,079,014 with the exception that this patent describes positive charge control agents containing a diazo type material. Other charge control agents are also known, such as alkyl pyridinium compounds and their hydrates, disclosed in U.S. Pat. No. 4,298,672.
While many of the prior art charge control additives are suitable for specific purposes, there continues to be a need for the development of improved charge control additives. In particular, a number of the prior art charge control additives interact with certain fuser rolls used in electrostatographic imaging systems, such as Viton fuser rolls, which causes such rolls to be adversely affected, thereby resulting in the deterioration of image quality. For example, Viton fuser rolls discolor and turn black as well as develop multiple surface cracks when certain prior art charge control additives are employed in the toner mixture. Further, some of the prior art charge control agents do not have the appropriate admixing times over extended periods.
One Viton fuser roll used in electrostatographic copying machines, particularly xerographic copying systems, is comprised of a soft roll fabricated from lead oxide and duPont Viton E-430 resin (a vinylidene fluoridehexafluoropropylene copolymer). This roll can be prepared by blending together followed by curing on a soft roll, approximately 15 parts by weight of lead oxide, and 100 parts by weight of Viton E-430. Apparently, the function of the lead oxide is to generate unsaturation by dehydrofluorination for cross-linking, and to provide release mechanisms for the toner composition. Excellent image quality has been obtained with the use of Viton fuser rolls, however, in some instances, there is toner fuser compatibility problems, when charge enhancing additives are part of the toner mixture. Thus, for example, it appears that certain charge control additives, such as quaternary ammonium compounds, and some alkyl pyridinium compounds, react with the Viton fuser roll. For example, an alkyl pyridinium chloride, such as cetyl pyridinium chloride when part of the toner mixture, appears to be catalytically decomposed by the lead oxide contained in the fuser roll, resulting in a higher unsaturated compound, which polymerizes and condenses with the unsaturated Viton. As a result, the Viton fuser roll turns black and develops multiple surface cracks resulting in image quality deterioration.
Some of the prior art charge enhancing additives while suitable for toner compositions to be utilized in the development of black images, may also not be suitable for the development of colored electrostatic latent images. Accordingly, there continues to be a need for toners and developer compositions which contain improved charge enhancing additives, and which compositions can be utilized for the development of electrostatic latent images, including the development of electrostatic color images. Further, there continues to be a need for positively charged toner materials for use in electrostatographic imaging systems employing Viton type fuser rolls, in order that high quality images can be produced over extended periods of time without adversely affecting such rolls. Additionally, there continues to be a need for toner and developer compositions which will rapidly charge new uncharged toner compositions being added to the charged developer, which toners are humidity insensitive as well as being compatible with Viton fuser rolls. There also continues to be a need for toner and developer compositions which possess high positive triboelectric charging properties for extended periods of time.